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How to check if a variable is set in Bash?

... (Usually) The right way if [ -z ${var+x} ]; then echo "var is unset"; else echo "var is set to '$var'"; fi where ${var+x} is a parameter expansion which evaluates to nothing if var is unset, and substitutes the string x otherwise. Quotes Digression Qu...
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Scala list concatenation, ::: vs ++

... edited Aug 25 '14 at 21:22 Zoltán 18.3k1010 gold badges7878 silver badges120120 bronze badges answered Jul 2 '11 at 23:15 ...
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Complex numbers usage in python [closed]

...(2,3) (2+3j) A complex number has some built-in accessors: >>> z = 2+3j >>> z.real 2.0 >>> z.imag 3.0 >>> z.conjugate() (2-3j) Several built-in functions support complex numbers: >>> abs(3 + 4j) 5.0 >>> pow(3 + 4j, 2) (-7+24j) The standar...
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How do browser cookie domains work?

...m 14.6k2020 gold badges7070 silver badges105105 bronze badges answered Jun 30 '09 at 13:43 GumboGumbo 572k100100 gold badges725725...
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Awaiting multiple Tasks with different results

... 190k2323 gold badges279279 silver badges394394 bronze badges answered Jun 19 '13 at 17:42 Stephen ClearyStephen Cleary 349k6363 g...
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Moment js date time comparison

...ror in the first line: var date_time = 2013-03-24 + 'T' + 10:15:20:12 + 'Z' That's not going to work. I think you meant: var date_time = '2013-03-24' + 'T' + '10:15:20:12' + 'Z'; Of course, you might as well: var date_time = '2013-03-24T10:15:20:12Z'; You're using: .tz('UTC') incorrectly....
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parseInt(null, 24) === 23… wait, what?

... messing around with parseInt to see how it handles values not yet initialized and I stumbled upon this gem. The below happens for any radix 24 or above. ...
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Associativity of “in” in Python?

...ith 'a' # throws Error coz (False in 'a') is # TypeError 15 RETURN_VALUE In [153]: def func2(): .....: return 1 in ([] in 'a') .....: In [154]: dis.dis(func2) 2 ...
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What is Robocopy's “restartable” option?

robocopy /Z = "copy files in restartable mode". 1 Answer 1 ...
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Java string to date conversion

...er 55 S Millisecond Number 978 z Time zone General time zone Pacific Standard Time; PST; GMT-08:00 Z Time zone RFC 822 time zone -0800 X Time zone ISO 8601 time zone -08; -0800; -08:00 Note ...